manuals: Add script to update vtr/counter documentation from docker

Run it like this:
COMMIT=master DOCKER_PLAYGROUND=~/scm/osmo/docker-playground OSMO_INTERACT_VTY=~/scm/osmo/osmo-python-tests/scripts/osmo_interact_vty.py ./regen_doc.sh

COMMIT will default to current HEAD.
Change-Id: Iedd1f55d021231d86c19b6f14ff296e3a55148c8
Related: OS#1700
diff --git a/doc/manuals/Makefile.am b/doc/manuals/Makefile.am
index 49ddc18..6542393 100644
--- a/doc/manuals/Makefile.am
+++ b/doc/manuals/Makefile.am
@@ -9,6 +9,7 @@
     message-sequences \
     mgw \
     om2000 \
+    regen_doc.sh \
     vty
 
 if BUILD_MANUALS